I am using Adobe captivate 5.5. I have a series of actions on a slide, and I wish that they could be replayed if the learner hits the "replay" button. In order to do this, I want to assign the action of Jume to slide (the current slide) to the "replay" button, so that the playhead can be reset to the beginning of the slide and everything can start over. However, the list of slides for this replay button doesn't include the current slide. I remember doing this in another situation and it worked fine.

You are correct that the default list of slides available to jump to does not include the current slide. If you remember doing this before, it may have been in a different authoring application.

If you want to replay the current slide from the beginning, there are ways to do it using variables and advanced actions. But the only way you'll be able to change the default behaviour of the Replay button on the playback bar is by using ActionSript 3 coding.

I just checked the project I did before where I was able to jump to the currect slide. It turned out that: if you directly assign the button to jump to slide on the properties panel, it won't include the current slide on the slide list; however, if you assign an "advanced actions", and add "jump to slide" in that advanced action script, then the current slide will be available in the slide list. Very interesting.